Oritavancin Potent Against Serious, Invasive S aureus Infections in European Hospitals

Oritavancin, known for its convenient 1-time dosing, is effective against skin and soft tissue infections, particularly involving serious gram-positive bacteria. Investigators at JMI Laboratories sought to determine whether oritavancin was also efficacious against a contemporary collection of Staphylococcus aureus isolates causing serious infections in hospitalized patients in Europe.

In a poster presented at the European Congress of Clinical Microbiology and Infectious Diseases (ECCMID 2019), the research team detailed their study, involving a total of 1232 S aureus isolates collected from invasive infections at 33 medical centers in 13 European and adjacent countries and regions in 2017-2018. Infections included bloodstream infections (BSIs; 77.8% of all isolates), followed by pneumonia (17.2%), bone and joint infections (BJIs; 3.1%), and intra-abdominal infections (IAIs; 1.9%).

Using Clinical and Laboratory Standards Institute and EUCAST breakpoints for susceptibility, investigators demonstrated that oritavancin (MIC₅₀/MIC₉₀, 0.03/0.06 mg/L) inhibited all S aureus isolates at ≤0.12 mg/L (susceptible breakpoint). Against methicillin-resistant S aureus (MRSA) and methicillin-susceptible S aureus (MSSA), oritavancin yielded similar MIC₅₀ (0.03 mg/L) and MIC₉₀ (0.03-0.06 mg/L) results regardless of infection type.

The MIC values remained at 0.03/0.03-0.06 mg/L despite the rates of MRSA varying greatly among European countries (0%-46.6%).

“MSSA isolates showed high overall susceptibility rates (≥98.0%) to oritavancin, vancomycin, teicoplanin, linezolid, and clindamycin,” investigators reported. “These agents, except clindamycin, remained active against MRSA isolates, regardless of infection type; however, oritavancin had MIC₅₀/MIC₉₀ results 16- to 32-fold lower than vancomycin, teicoplanin, and linezolid.”

In all, 3 S aureus isolates displayed teicoplanin resistance (MIC >2 mg/L), 2 showed vancomycin MIC results of 2 mg/L, and all 3 were inhibited by oritavancin MIC values between 0.03 and 0.12 mg/L.

“The lipoglycopeptide oritavancin remained potent against S aureus, including MRSA, causing serious infections in European medical centers and surrounding regions,” investigators concluded. “Its prolonged half-life and high potency may support oritavancin as a good option for treating serious S aureus infections.”

The study, “Oritavancin Activity Against Staphylococcus aureus Clinical Isolates Causing Serious Infections in Hospitalized Patients in Europe (2017-2018),” was presented in a poster session on Monday, April 15, 2019, at ECCMID 2019 in Amsterdam, the Netherlands.